Automatic starting electrical control circuit for engine driven electric power generators



Sept. 23, 1952 R WALTERS 2,611,877

AUTOMATIC STARTING ELECTRICAL CONTROL CIRCUIT FOR ENGINE DRIVEN ELECTRIC POWER GENERATORS Original Filed June 8, 1948 'LO LO M x 2 o U m z 5 U INVENTOR.

v BY

Mala i 0 ATTORNEY Patented Sept. 23, 1952 AUTOMATIC STARTING ELECTRICAL CON- TROL CIRCUIT FOR ENGINE DRIVEN 1 ELECTRIC POWER GENERATORS] Robert E. 'Walters, Milwaukee, Wis., assignor to Allen-Bradley Company, Milwaukee, Wis., a" corporation of Wisconsin Continuation of application Serial No. 31,797,

June 8, 1948.

1951, Serial No. 251,099

My invention relates in general to an automatic-starting electric control circuit for engine driven electric power generators, and in particular to a combination-of devices arranged to oper-- ate on a loW current and to withstand the comparatively high current.

In automatic-starting electric power generators it is necessary to provide a current'sensitive I electric circuit which is a combination and an arrangement of standard-component parts sensitive to small currents and able to withstand comparatively large currents and to do so in an efficient electrical manner. It is also an object of my invention that the electric circuit and its parts shall be comparatively small in physical dimensions, shall be reasonably cheap to manufacture and shall be reliable and have ease of adjustment.

This application is a continuation of my co-pending application entitled Electric Control Circuit," Serial Number 31,797 filed in the United StatesPatent Ofiice June 8, 1948.

My invention relates more specifically to an apparatus-including a transformer circuit having its primary energized by the load circuit, and the secondary circuit including therein the coil of an electromagnet of a control relay and a suitable capacitance.

In this arrangement the power factor of the secondary circuit at the minimum operating primary current of the transformer is relatively high" which results in a higher overall efficiency and a smaller transformer to do the same work.

My invention is exemplified in a control relay circuit which in-conjunction with other elements of the power plant circuits is operable to start and'stop a self-contained electric lighting plant, that is, a plant with generator and prime mover. On the closing of the load circuit which may be carrying only a single lamp a small direct current flows of the order of '75 milli-amperes through the coil of the electromagnet. This current causes the electromagnet to go to its closed position and a short period thereafter an alternatingcurrent of theorder of one quarter of an 9 Claims. (01. 290 .-so

This application October 12;

ampere flows from the generator through; the? primary of the transformer, andthe secondary circuit :in which the electromagnet is connected". has in. it an alternating current of the order 20f? 30milli-amper'es, and which current issufiicient a to hold the relay in its closed position. With the lighting plant in operation additional load may be thrown into the circuit and'a maximum of l amperes may becarried'through the primary 'cir="= cuit 'of the transformer? It is evident from the foregoing that the primary of the transformer My invention, therefore, is'the procurementof'an" arrangement whereby a smaller transformer'm'ay'i 15 'be used to keep the relay in its closed position and still cause no burn-out in the operatin'g'coils; of said transformer and electromagnet and alsotosecure better efficiency in the operationfof the is carrying currents in therati'o of to 1'.

relay.

- The secondary load circuit'is so arranged that its power factor is relatively high and as a result" the size of transformer required, interms of minimum primary operating current, is reduced? The transformer is designed so that at the higher 'primary current values its iron circuit becomes saturated, which in turn reduces th'eratio of pri' mary to secondary transformation;

It" will alsobe noted that my invention provides a' circuit' in which the coil of the electromagnet isenergized by a direct current connectionand that thereafter alternating current is suppli'edto the coil and that 'no-breakdsimade in'the' transformer secondary 'circuit' at anytime. In an explanation of my invention incorporated --in an electriclighting plant; the single figureof the drawing is a wiring diagram of the power" and control connections with component parts.

In describing the operation of this electric; lighting plant the usual conditionis assumed that is to say that power disconnect switch designated by the numeral II is in the on position, magneto switch 12' for magneto 93 is in th'e'closed' or automatic position and the controldisconnectfi switch l3'is in on position. When a load of 40 watts or more designated by the numeral I4 is" connected to th'ealternating current lines l5 and I 6 by the closing of 3 switch l1, the current from? the battery I31 flows through conductor l9, through contact 23 of power disconnectfl l, through conductors 2t and 21, through the con tacts of control disconnect l3, through conductor 22; through the contacts 24 of thermal timing relay 25, through conductor 25, through contacts 2'! of main switcl'i; 28, through conductor- 29;? through the coil 3il-of control relay 31-, through conductor 46, through the secondary 32 of transformer 33, through conductors 34 and 35, through the contacts 36 of power disconnect H, through conductors 31 and 38, the contacts of switch [1, conductor 39, load l4, conductors 40 and 4|, contact 42 of power disconnect ll, conductors 43 and 44 to conductor 45, back to the other terminal of the battery 18.

On the operation of control relay 3| the normally open contacts 41 close and the current flows from the battery 18 through conductor I9, through the contacts 23 of power disconnect H, through conductors 20 and 2|, switch contacts of control disconnect l3, conductor 22, contacts 24 of thermal timing relay 25, through conductor 48, through the normally closed contacts 49 of reverse current relay 50, through conductor through the coil 52 of starting relay 53, through conductor 54, through the normally open contacts 41 of control relay 3| and thence back to the battery through conductors 55 and 45.

It is to be noted that in the last circuit described coil 52 of starting relay 53 was energized. The'automatic choke 58 is also energized through conductors 51 and 58. Also likewise the resistance .unit 59 of thermal timing relay 25 is energized through conductors 60 and El. When the control relay 3| operates the normally closed contacts 62'open the magneto circuit. As the starting relay 53 is operated its normally open contacts 63 close and the current flows through these contacts from the battery and through conductor 64, through the coil 65 of reverse current relay 50; through conductor 56, through the series field 61 and armature 68 of the exciter B9 andback'through the conductor 45 to the bat tery;

It-is also to be noted that in the same manner a circuit has been established through the shunt field and through the shunt field resistor 1|. The shunt coil 13 of the reverse current relay 50--is energized from the batterv circuit through conductors 14 and 15, but at this time the relay does not operate. The coil 16 of the main switch 281s energized from the battery circuit by conductors 11 and 18, but this relay does not operate at this time. The current flowing in the series coil 65 of reverse current relay 50 neutralizes the effect produced by the shunt coil 13-and the relay cannot therefore operate immediately.

The 'exciter 69 has its shaft connected to the shaft of the alternator indicated by the numeral 19, and the exciter acts as a motor to bring the alternator and connected engine indicated by the numeral 80 up to cranking speed. When the engine starts supplying power to the system and its speed increases, the current in the series coil 65 of the reverse current relay 5!] approaches zero as the exciter develops a voltage equal to the battery voltage, and with the neutralizing efiect of the series coil 55 at the low value the relay will operate. When the contacts 49 of relay 50 open, the circuits to the automatic choke 56, the coil 52 of starting relay 53 and the resistance unit- 59 of the thermal timing relay 25 are opened. At the same time the normally open contacts 8| of relay 50 close and connect the exciter 89 to the battery, through the charging resistor 82.

This-latter circuit is from one terminal of the exciter 69 through conductor 45 to the negative terminal of battery I8 and the other portion ofthe circuit is from the exciter, through series field 61, conductor 66, coil 85 of relay 50, congine speed increases and approaches its governor setting the exciter which is now a generator increases its voltage and the main switch 28 operates as its coil 18 is connected to the conductors 63 and 45 leading from the exciter or generator as it new functions. When the normally open contacts 810i the main switch 28 close the load is operated with alternating current voltage. The load current'fiowing through the primary 89 of the transformer causes the coil of the control relay to be energized with alternating current voltage produced in the secondary 32 of the transformer. This circuit is from the secondary 32 of the transformer through conductor l0l,

capacitor I04, conductor I02, coil 30 of control' relay 3 I, through conductor 46 back to the transformer secondary 32. Therefore the control relay remains closed. By the operation of contact 21 of the main switch 28 the alternating current and direct current circuit are separated.

The plant continues in operation as long as.

theload current is suflicient to hold the control relay closed. When the load current is decreased below the value required to maintain the control relay in the energized position this relay operates to its open position and the contacts 52 close causing the primary circuit of the magneto to be short-circuited. With the magneto short circuited the engine cannot supply power and its speed decreases. The alternating current voltage then decreases in magnitude and frequency and the direct current generated voltage also de-' creases. When the direct current generated voltage falls to approximately battery voltage the main switch 28 operates to its open position and the load is then disconnected from the alternat ing current generator circuit. The contacts 21 of relay 28 are closed and the control circuit is set up for the next starting cycle. The engine speed continues to decrease and the generated voltage falls to a still lower value and the reverse current relay 50 operates. When the normally open contacts of the reverse current relay open, the generator and charging resistor are separated from the battery and its normally closed contacts close and complete the starting control circuit. The plant then falls to zero speed.

It is to be noted that during the starting cycle the circuit across the terminals of magneto 93 is through conductors 94 and 96, magneto switch l2, conductor 91, normally closed contacts 32 of control relay 3|, through conductors 55, 45 and 12 back to magneto. During normal operation, on the occurrence of an overload the magneto has a circuit completed across its terminals through conductor 34, contacts 98 of overload relay 85, conductors 95, 45 and 12 back to the magneto.

In the above description in which typical values of actual working conditions were assumed the normal operation of the starting and running of a self-contained lighting plant is explained embodying my invention. It is to be noted that, that part of the circuit which embodies my invention is composed of a transformer, a capacitor and an electromagnetically operable relay. These component parts are chosen and so arranged that in this particular case only a very small flow of comparativelyhigh load maycontinue tot-flown without any change inth'e control circuits, Also,

it -is to' be noted that the oomponent parts with 5 the arrangement and' coordination-of par-ts' pro duce'an elficient 'control in that tliere i's not undue" powerloss in the transro'rmerpniagnet coil of .tlie relay and in th'e capacitorl I "aving described a particula'r application? of my: invention it is intended protection i tofl be affordedi'herebyextendmto: the 111111 limit ot the inventive advance her'ei disclosed and as dea finecr by' the claims' hereto appendedi '1'; ln an automatic electric power plant an internal combustion engine an alternating cure: ren't generator connected theretozrto' bendriv'en thereby; an alternating current load circuitfcona nected' to-said =generator adapte "to be closed through a load-i' a storage: batter an electro Y magnetic switch-havinga coil and contacts actu-T- ated thereby a directcurrent energizing circuit: extending from said b'attery' through said coil ito said loadcircuit and returning therefrom toisaid r battery? said:energizing circuit-being adapted-to be closedhy"imposition of a load upon said load circuit"; i a tra'nsformer having a low impedance primary interpo's'ed' in series'firelationin said load circuit an'd having a' saturable frame :and': a sec-1. ondary winding; a maintaining circuit: fort-said electro-magneticswitch means comprising acapacit'anc'e and 'circui't. connections joining said, transformer secondary 'said capacitance and-"said coil in' closed serieswonnection; a starting motor drivingly' connected to said engine; anda starting cireuit extending i from said batteryrto' said start ing 'motorg said starting circuit being closeable in response toactuation of the 1 contacts of said" electro-magnetic switch.

Z-L In' an 1 electric power plant an -'alternating current generator; an internal: cornbustion engine-dr'ivingly' connected to said -generator; a dynamo 'electri'c apparatus connected to saidilerrgin'e to' dr'ive and: start th'e same andto be" driven i a's a direct current generator by saiden'gine when started;" a load circuit connected 'in load 'receivin'g relationto said alternating current gene'r ator; a control transformer having aprimary winding inter-posed in load-"carryingseriescon nection in said load circuit; u said transformer" having a satu rable frame and a secondary: win'd' ing';-' a control relay' having a" coil 'and normally open" contacts operable thereby; a control relay maintaining'circuit comp'rising' a blocking con-"- denserand leads joining said transformer v Lse'c-' on'd'ary winding, said may-e011 and said-blocking condenser in closed series circuit to-causesaid relay -tobe 'inaintained closed :when' saicl'load leads are carrying a load; a direct-current source including a storage-battery and circuit connec tionsext'ending' therefrom to said dynamo elecl tric apparatus; a control relay energizing circuit" comprising connections between said direct current source through said relay coil to' saidload" leads whereby said relayenergizing circuit is. completed to close saidrelay whenever said load circuit is closedby'xa load; and-a starting and running"- circuit including switch means interposed in said'direct current-source circuit closeable to complete the same in response to closure of said-control relay contacts. I

3: In' a control apparatus for an electric-power plant of the type which includes an alternatin'g current'generator; an internal-combustion enginedrivingly f connected; 1:01 :saidLLgenerator; and

dynamo-electricapparatusiconnected;totsaidien W- gine to Idrive'and -start'the same andto'beidrivenn asa direct current generator by said enginei'whens started which control apparatus-Lv comprises load: lea'dshaving h input terminals adapted to be cont-J. nected' in loadreceiving relation to said' alternates. ing current-generator andflhaving output terml nals at" their opposite ends adapted to supply" alternating current to a load connected thereto: acontrol transformer having a primary winding interposed in load carrying series connection int one of said load leads-said transformerhaying' a saturable frame and a secondary"windingya control relayhaving a coil and normally open: contacts operable thereby; a control relay mainta'ining': circuit comprising a blocking condenser and leads joining said transformer secondary" windingfsaid relay coil and said blocking condenser in closed series circuit to cause said relay to be maintained closed when said'loadleadsare carrying a load; a direct current source circuit including battery terminals adapted to be con-' nected to a storage'battery and circuit 'connections extending'therefrom to terminals adapted" to be connected to said dynamo-electric appa ratus;'a control relay energizing circuit com-' prising connections between said direct current source'th'rough said relay coil to said lead, leads whereby said relay energizing circuit is completed to close said relay Whenever said load circuit'is" closedby a load; and a starting and running" circuit including switch means interposed insaid" direct current sourcecircuit closcable to complete the same'in response to closure of. saidcontrolv relay contacts. t r o l 4; In a control apparatus for an electricpower" plant of the type whichincludes analternating current generator, an internal combustion engine) drivingly connected to said generator, and a dynamo-electric apparatus connected to said enegine to drive andstart'the same and to be driven as a direct current generator by said engine: when started which control apparatus comprises". a load circuit having input terminals adapted to be connected in load receiving relation. to said alternating current generator and having'out put terminals adapted to supply alternating cur-1 rent to a load connected thereto; a normally open output responsive load switch interposed in;

said load circuit including means operative to close said loadswitoh when said alternating cur! rent generator is being driven; a control trans? former having a primary winding 'interposed in" load carrying series in. connection invsaidfload circuit, said transformer having a satura blel, frame and asecondarywinding; a vcontrol relay having a coil and normally open contacts operable thereby; a control relay' maintaining." circuit comprising a blocking condenser and leads joining said transformer secondary" wind in'g, said relay coil'and said blocking condenser in closedseriescircuit to cause saidrelayfto' be maintained closed by alternating current" when,

' said loadcircuit'is"carrying a load; a directcu'r' rent source circuit including battery terminals adapted-to be connected to a storage battery and" circuit connections extending therefrom to ter minals adapted to be connected tosaid dynamo -j' electric apparatus; a control relay energizing cir cuit' comprising connections between said direct, current source circuit through said relay coi-l tb' haid load circuit, "said energizing circuit' inclu'ding an electro-re'sponsive switch "means *o pene by current' 'generated by said dynamo-electric machine whereby said relay energizing circuit'is completed toclose said relay whenever a load is'joined across said output terminals and is opened when said dynamo-electric machine starts generating; and a starting and running circuit including electromagnetically actuated switch means interposed in said direct current source circuit closeable to complete the same in response to closure of said control relay contacts.

5. In a control apparatus for an electric power plant of the type having a load circuit including leads, an alternating current generator in current supplying relation to said load circuit, a prime mover drivingly connected to said generator, and a dynamo-electric apparatus connected to said prime mover to drive and start the same and to be driven as a direct current generator by said prime mover when started, which control apparatus comprises in combination terminals adapted to be connected to a storage battery to provide a direct current source; a control relay having a coil and contacts operable thereby; a relay coil energizing transformer having a primary winding adapted to be interposed in said load circuit leads and a secondary winding: transformer circuit connections joining said secondary winding of said transformer in circuit with said relay coil to maintain said relay closed when load is carried; switching means having coilmeans responsive to voltage of said dynamoelectric apparatus, said switching means having normally open line contacts adapted to be interposed in said load circuit to open and close the same and normally closed energizing circuit contacts; energizing circuit connections for said relay coil adapted to join said relay coil through said load circuit and said energizing circuit contacts to said direct current source to cause said control relay to be closed whenever a load is imposed by said load circuit; and starting and running circuit connections for said dynamo-electrio, apparatus including said control relay contacts adapted to join said direct current source to saidv dynamo-electricrapparatus to cause the same to drive and start said prime mover when said control relay is energized, whereupon said switching means becomes operative to close said linecontacts and to open said energizing circuit contacts upon occurrence of a generated output by said dynamo-electric apparatus.

6. In a control apparatus for an electric power plant of the type having a load circuit including leads and a manually operable starting switch, an alternating current generator in current supplying relation to said load circuit, a prime mover drivingly connected to said generator, and a dynamo-electric apparatus connected to said prime mover to drive and start the same and to be driven as a direct current generator by said prime mover when started, which control apparatus comprises in combination terminals adapted to be connected to a storage battery to provide a direct current source; a control relay having a coil and contacts operable thereby; a relay coil energizing transformer having a secondary winding and a primary winding adapted to be interposed in load carrying relation with said leads of said load circuit; transformer circuit connections joining said secondary winding of said transformer in circuit with said relay coil to-rnaintain said relay closed when load is carried; switching means having coil means responsive to voltage of said dynamo-electric apparatus, said switching means having normally openline-contacts adapted to be interposed in said load circuit-to open and close the same and normally closed energizing circuit contacts; energizing circuit connections for said relay coil adapted to join said relay coil through said load tacts and to open said energizing circuit contacts upon occurrence of a generated output by said dynamo-electric apparatus.

7. In a control apparatus for an electric power plant of the type having a load circuit including leads,-an alternating current generator in current supplying relation to said load circuit, a prime mover drivingly connected to said generator and a dynamo-electric apparatus connected to said prime mover to drive and start the same and to be driven as a direct current generator by said prime mover when started, which control apparatus comprises in combination terminals adapted to be connected to a storage battery to provide a direct current source; a control relay having a coil and contacts operable thereby; a relay coil energizing transformer having a primary winding adapted to be interposed in load current carrying relation with said leads of said load circuit and a secondary winding; a blocking condenser; transformer circuit connections joining said secondary winding of said transformer in series circuit with said relay coil and said blocking condenser to maintain said relay closed when load is carried; switching means having coil means responsive to voltage of said dynamo-electric apparatus; said switching means having normally open line contacts adapted to be interposed in said load circuit to open and close the same and normally closed energizing circuit contacts; energizing circuit connections for said relay coil adapted to join said relay coil through said load circuit, said secondary winding, and said energizing circuit contacts to said direct current source to cause said control relay to be closed whenever a load is imposed by said load circuit; and starting and running circuit connections for said dynamo-electric apparatus including said control relay contacts adapted to join said direct current source to said dynamoelectric apparatus to cause the same to drive and start said prime mover when said control relay is energized, whereupon said switching means becomes operative to close said line contacts and to open said energizing circuit contacts upon occurrence of a generated output by said dynamoelectric apparatus.

8. In a control apparatus for an electric power plant of the type having a load circuit including leads, an alternating current generator in current supplying relation to said load circuit, a prime mover drivingly connected to said generator and a dynamo-electric apparatus connected to said prime mover to drive and start the same and to be driven as a direct current generator by said prime mover when started, which control apparatus comprises in combination terminals adapted to be connected to a storage battery to provide a direct current source; a control relay having a coil and contacts operable thereby; a relay coil energizing transformer having a primary winding adapted to be interposed in load carrying relation with said leads of said load circuit and a secondary winding; transformer circuit connections joining said secondary winding of said transformer in circuit with said relay coil to maintain said relay closed when load is carried; a load line contactor having a coil responsive to voltage of said dynamo-electric apparatus, said load line contactor having normally open line contacts adapted to be interposed in said load circuit to open and close the same and normally closed energizing circuit contacts; energizing circuit connections for said relay coil adapted to join said relay coil through said load circuit and said energizing circuit contacts to said direct current source to cause said control relay to be closed whenever a load is imposed by said load circuit; a dynamo-electric apparatus contactor having a coil and normally open contacts operable thereby; dynamo-electric apparatus contactor coil circuit connections adapted to join said dynamo-electric apparatus contactor coil through said control relay contacts when closed to said direct current source whereby said dynamo-electric apparatus contactor contacts are closed upon energization of said control relay; dynamo-electric apparatus circuit conneca tions adapted to join said dynamo-electric apparatus through said dynamo-electric apparatus contactor contacts to said direct current source to cause the same to drive and start said prime mover when said control relay is energized; and

load line contactor circuit connections adapted to join said load line contacts and to open said energizing circuit contacts upon occurrence of a generated output by said dynamo-electric apparatus.

9. In a control apparatus for an electric power plant of the type having a load circuit including leads, an alternating current generator in current supplying relation to said load circuit, a prime mover having a magneto drivingly connected to said generator and a dynamo-electric apparatus connected to said prime mover to drive and start the same and to be driven as a direct current generator by said prime mover when started, which control apparatus comprises in combination terminals adapted to be connected to a storage battery to provide a direct current source; a control relay having a coil and a pair of contact sets operable thereby said first set being normally open and the second set being normally closed; a relay coil energizing transformer having a primary winding adapted to be interposed in said load circuit leads and a secondary winding; transformer circuit connections joining said secondary winding of said transformer in series circuit with said relay coil to maintain said first set of relay contacts closed and said second set of relay contacts open when 10 load is carried; switching means having coil means responsive to voltage of said dynamoelectric apparatus, said switching means having normally open line contacts adapted to be interposed in said load circuit to open and close the same and normally closed energizing circuit contacts; energizing circuit connections for said relay coil adapted to join said relay coil through said load circuit and said energizing circuit contacts to said direct current source to cause said control relay to be closed whenever a load is imposed by said load circuit; a magneto contactor having normally open contacts and a coil adapted to be interposed in load carrying relation with said load circuit leads to cause the contacts to close upon an overload of predetermined value passing therethrough; magneto circuit connections including said magneto contactor contacts and the second set of said control relay contacts adapted to be joined to said magneto whereby said magneto is short circuited upon itself through said contacts of said magneto contactor when closed and is short circuited upon itself through the second set of said relay contacts when closed; and starting and running circuit connections for said dynamo-electric apparatus including the first set of said control relay contacts adapted to join said direct current source to said dynamo-electric apparatus to cause the same to drive and start said prime mover when said control relay is energized, whereupon said switching means becomes operative to close said line contacts and to open said energizing circuit contacts upon occurrence of a generated output by said dynamo-electric apparatus.

ROBERT E. WALTERS.

REFERENCES CITED The following references are of record in the file of this patent:

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